The present invention relates to the field of motor-vehicle brakes. More precisely, the invention relates to an improved structure of a subassembly of a brake actuator that has been provided for an electromechanically operated parking brake or an electromechanically operated service brake.
Electrically operated parking brakes (EPB) are increasingly replacing conventional parking brakes, which via cables convert a force applied by the driver into a locking force at wheel brakes of the vehicle. The advantage of electric parking brakes lies in their capacity to be driven by modern on-board electronics. As a result, new application options for the parking brake are opened up, such as, for example, the realisation of a hill-start assist (hill-hold function).
An electrically operated parking brake includes, as a rule, an electromechanical brake actuator which exerts a locking force at the wheel brakes via a mechanically displaceable brake piston. The brake actuator is substantially defined by a subassembly, including motor devices and gearing devices, that has been supported in cushioning manner in a housing and has been accommodated in the interior of a vehicle wheel.
A particular challenge now consists in constructing a high-performance, low-wear and, at the same time, spatially compact electromechanical brake actuator, in order to save weight and space. With a view to enhancing performance, in this connection a multi-stage gearing is frequently employed, in order to obtain a considerable gear reduction of the rotational motion generated by the electric motor (a typical gear-reduction value is 120:1). With increasing complexity of the gearing, however, the wear potential of the brake actuator rises, by virtue of which, in turn, the service life of the brake actuator is impaired.
From patent application DE 10 2004 048 700 A1 an electromechanical brake actuator is known that exhibits an electric motor and a three-stage gearing device. The gearing device includes two successive toothed-wheel gearing stages, downstream of which on the output side a planetary gearing stage has been connected. Furthermore, two gearing shafts, supported on one side of a carrier element, for the support of the two toothed-wheel gearing stages and of a sun gear of the planetary gearing stage have been provided.
The construction and stable mechanical support of the gearing components is crucial, in order, on the one hand, to reduce the volume of the brake actuator and, on the other hand, to extend its service life. For example, an inadequate support of greatly loaded gearing components may intensify the wear in the gearing, by virtue of which the service life and the efficiency of the brake actuator decline.